I am building a Greenland SOF kayak from Mark Starr's book. I've made some mistakes, but I am convinced that, at worst, it's going to float!

My question is, the aft deck beam (isserfik) has ended up about 2cm below the deck as defined by the apummaqs, as are the other deck beams. The photos in the book look the same (figs 1.9, fig 4.8). However, some of the drawings make it look as if the beam should be flush with the deck (figs 1.2, 5.14).

My question is, if the deck fabric is going to run under the cockpit coaming, either the coaming is going to "float" above the aft beam, or if I lash the coaming down, there will be a substantial depression between the bottom of the coaming and the rest of the deck as defined by the aft stringers and apummaqs.

Should I attach a shim under the coaming? that would also let the forward end of the deck stringers run right up and level with the bottom of the coaming.